Troubleshooters, Essentials, Update, Defender not working

I've tried to post a reply but for some reason it became Threadstarter, so I've deleted it and now I can't post it again, because Sevenforums says that it's a copy of another post... etc. I'm trying to past it below. Here it is:

I really don't wont to do this until I'll run out of ideas. But I've just remembered something: during previous reinstallation I've change User directory location - moved it to second partition using Sysprep. Could that be a reason of my problems? I don't remember having any troubles back then, when User directory was on partition without OS.

But I've just read this:

Don't move your Windows user profiles folder to another drive | ZDNet

...and I start to wonder.

Sorry. I don't know how it all works on this forum. Hence the problems with posting reply. I feel stupid now that I've understood my mistake.

Try moving the User profile back to C using Method Two here: User Profile - Change Default Location

If you have a space issue you can first copy the data out of some or all User folders (Documents, Pictures, Desktop, etc) to the data drive. Later you can set up a second set of data folders on the data drive and either move the active User folders to them or link them to their related Library - Include a Folder setting that data folder to be the default save location: Library - Set Save Folder.

The common issue which requires linking to Libraries instead of moving User folders is if you want to use Win7 backup imaging, which will force you to include the data drive User folders in a backup image. If you don't use it then you can move the User folders without issue that we've seen.

Let us know how this goes.

I meant that I've moved it to second partition during former installation, not the latest one. Then I've reinstalled Windows again without using sysprep (so User directory is currently on system partition again). I just wonder if it might have left some traces on my computer that are now preventing Windows Update from running properly.

Pardon my English. I'm not native speaker.

Did you correctly delete all partitions during the reinstall?

Have you looked over the steps which compile everything to consider to get and keep a perfect install, to see how close you came with your reinstall? If not then I'd do it over, and this time delete all partitions during the booted Clean Reinstall - Factory OEM Windows 7

It was my dad who performed the latest reinstallation. And he doesn't remember how he did it. So I guess he must have made some mistake. I'll probably do it once more then.

One more question: would I be able to use same registration key? Because Microsoft gives me only one registration key for each software they offer under the terms of MSDN AA program I've mentioned above. In other words: can I reinstall my Windows 7 for free?

Thanks. I'll do that. Not in the next few days though. I'm constantly out of time.

PS. Andrew: why not activate at once?